Date of Award:

5-1968

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geosciences

Department name when degree awarded

Geology

Committee Chair(s)

Robert Q. Oaks Jr.

Committee

Robert Q. Oaks Jr.

Committee

Clyde T. Hardy

Abstract

When Lake Bonneville spilled through Red Rock Pass at the north end of Cache Valley, the major part of the lake in Salt Lake Valley had to drain from west-to-east through Cutler Dam Quadrangle. Here two major saddles connect the two valleys: (1) Bear River Narrows, at about +4380 feet; and (2) Cache Butte-Wellsville Mountain Pass 4.2 miles south, at about +4970 feet. Spillover levels at both places are cut into older rocks.

Only two morphostratigraphic units are recognized widely in the quadrangle. These represent high stands at the Bonneville level (+5180 ± 20 feet) and at the Provo level (+4800 ± 20 feet). Regressive shoreline deposits extend continuously from the Provo level down to the Stansbury level (+4470 ± 20 feet). The older Alpine level (Morrison, 1965) is not clearly represented. A well developed gravel bar with a flat crest near +4940 feet immediately southeast of Bear River Narrows indicates a period of east-to-west flow through the narrows when the lake level stood briefly below the level of both Red Rock Pass and of the pass farther south.

The following history is inferred:
1. Rise of lake to Bonneville level (+5180 feet) or slightly higher;
2. Spillover and downcutting at Red Rock Pass to a point above +4940 feet; eastward flow through Bear River Narrows and Cache Butte-Wellsville Mountain Pass;
3. Red Rock Pass abandoned; westward flow through Bear River Narrows only as the lake level continued to fall; lowest point unknown;
4. Rise of lake above +4940 feet; spillover and renewed cutting of Red Rock Pass down to Provo level (+4800 feet); eastward flow through Bear River Narrows;
5. Rapid fall of lake level and abandonment of Red Rock Pass at +4755 ± 2 feet (Williams and Milligan, 1967); westward flow through Bear River Narrows continuous to present.

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